The present invention relates to a novel polydialkylsiloxane/polyamide copolymer, a process for producing the same, and to various materials such as ophthalmic materials such as contact lenses and intraocular lenses, medical materials such as antithrombotic materials, and a variety of cosmetic compositions or electronic materials formed with the copolymer.
Siloxane polymers typified by polydimethylsiloxane have excellent biocompatibility, gas permeability, and other functions, and their various uses in the medical field have been awaited, some of which have been brought into practice. However, conventional siloxane polymers have a problem in strength and therefore their uses are limited.
Under the circumstances, polymers having both an alkylamide group excellent in strength, particularly an aramid segment such as an aromatic polyamide (aramid), and a siloxane segment excellent in biocompatibility and the like are now under development.
For example, there has been proposed a complexed polymer formed by copolymerizing a siloxane polymer with aramid (Japanese Patent Application Laid-Open No. Hei 1-12384), and there have been disclosed that this polymer serves as an excellent biocompatible material (Japanese Patent Application Laid-Open No. Hei 2-203863 and Japanese Patent Application Laid-Open No. Hei 5-285216) and that this polymer can be utilized as a contact lens material (Japanese Patent Application Laid-Open No. Hei 6-313864).
According to the production method of the siloxane/aramid copolymers, such copolymers appear to be a material in which at least dozens of percentages of free amino groups remain at its ends. Moreover, since the aramid segment of the siloxane/aramid copolymer dissolves in a limited variety of solvent systems, the biocompatibility test which is carried out on each of these copolymers provides nothing but the evaluation results of the film molded therefrom according to the solvent casting method in which a solvent such as N,N-dimethylacetamide (hereinafter, abbreviated as DMAc), dimethylformamide (hereinafter, abbreviated as DMF), or the like is employed.
Generally, a molded article obtained according to the solvent casting method is made almost free from solvent by being subjected to a solvent-removing treatment comprised of heating the article to the glass transition temperature of the polymer or higher and lowering the pressure. However, when a solvent like DMF or DMAc having a high polarity and a relatively high boiling point is employed, removing the solvent to such an extent as is considered to be non-problematic in terms of the use as a medical material is extremely difficult. Therefore, for use as a medical material, it would be desirable that a copolymer is heat-moldable without using a solvent, and the copolymer is required to have a sufficient thermal stability.
However, the heretofore suggested complexed polydialkylsiloxane/polyamide copolymer formed by block-copolymerizing a siloxane polymer with aramid has a problem that, when heated to a certain temperature to evaporate the solvent completely or examine its fluidity upon heating after having been molded by the solvent casting method, it turns pale yellow and further browns. In addition, there is a problem that, due to crosslinking reaction, an attempt to dissolve the heat-dried copolymer in the same solvent again will result in failure. Furthermore, it has come to be known that there is a problem that heating the copolymer to high temperatures causes its liquid siloxane component to decompose and elute. Therefore, when heat-molding such polymer, sufficient care must be taken over the temperature control, heating time and the like. Further, such polymer is inapplicable to ophthalmic or medical materials, for not only is such polymer difficult to heat-mold, but also heat treatment for removing the solvent inevitably incorporated therein is arduous.
Surface and Interface Analysis, Vol. 10, p416-423 (1987) and Surface and Interface Analysis, Vol. 13, p233-236 (1998) report that plasma irradiation is carried out to render the surface of a contact lens made of an acrylate polymer having a siloxane side chain hydrophilic. Polymer Journal, Vol. 42, p841-847 (1985) also reports that a silicone rubber contact lens is subjected to plasma irradiation thereby to make its surface hydrophilic. However, there exists a problem that, even after such treatment, it is difficult for the lens to retain its hydrophilicity over a long period of time and that adhesion of protein onto the lens surface becomes considerable.
In Polymer Journal, Vol. 20, p485-491 (1988), it is reported that, as can be understood from the fact that the gas permeability of polydimethylsiloxane is not adversely affected even if it is subjected to electron beam irradiation at a dose of 80 Mrad, electron beam irradiation at a dose of 80 Mrad or so does not cause neither crosslinking nor decomposition in the chemical structure. On the other hand, in Adhesion, Vol. 34 p201-209 (1991), it is reported that, as a result of the swellability (solubility) test made on polydimethylsiloxane irradiated with an electron beam, polydimethylsiloxane was completely dissolved at 20 KGy (=2 Mrad) or less and that crosslinking was observed at 50 KGy (=5 Mrad) or more. The publication also says that such electron beam irradiation raises the storage modulus (Gxe2x80x2) and loss modulus (Gxe2x80x3).
These publications referred only to energy beam irradiation of siloxane polymers, and none of them touched on improvements in physical properties resulting from energy beam irradiation of a molded article of the polydialkylsiloxane/polyamide copolymer.
The above-mentioned polydialkylsiloxane/polyamide copolymer is what is constituted of siloxane chains into which, mainly for supplementing strength-related drawbacks of a siloxane polymer, aramid segments have been introduced as multi blocks. As compared to a molded article which is exclusively made of a siloxane polymer, its molded article fabricated by the solvent casting or heat-molding method has a largely improved strength as it is, which is due to the interaction between the aramid segments. However, with respect to the influence the aramid segment to siloxane segment ratio of the polydialkylsiloxane/polyamide copolymer exerts, its strength owing to aramid and such functions as oxygen permeability and biocompatibility due to siloxane are in a trade-off relation. Therefore, when aiming. for a still higher, well-balanced performance, its physical properties need to be improved not by varying the ratio but by other means.
A polyamide, due to its amide bonding, shows relatively good hydrophilicity. However, it has been known that, when a polyamide is complexed with a siloxane-type polymer as in the case of a polydialkylsiloxane/polyamide copolymer, the resulting material will be highly hydrophobic, which is because the mobility of its siloxane segments at the molecular level is good and thus the surface of the material is covered by the siloxane segments. Although not all the medical materials are required to be hydrophilic and whether hydrophilicity is a requisite or not depends on the intended use, for example, contact lens materials need to be hydrophilic in view of not only a good fit to the eye but also the prevention of a lens from, as a result of a long-time wear, clinging to the cornea of the eyeball. To give an example, silicone elastomer contact lenses have once been put into practical use, which resulted in failure because their hydrophilicity was insufficient.
Thus, for expanding the uses of a molded article of a highly hydrophobic polydialkylsiloxane/polyamide copolymer, it is necessary to impart hydrophilicity to the surface thereof. However, nothing has been heretofore proposed to improve the hydrophilicity of polydialkylsiloxane/polyamide copolymer molded articles.
On the contrary, copolymers having a phosphorylcholine derivative group have been studied from various aspect because of their excellent contamination resistance, hydrophilicity, and biocompatibility. For example, there have been known a process for providing a copolymer by copolymerizing a monomer having a phosphorylcholine derivative group, a process comprising coating a copolymer having the above-mentioned functional group onto a substrate, and a process comprising chemically bonding a copolymer having the aforementioned functional group to a material having a reactive group (Japanese Patent Application Laid-Open No. Hei 3-39309, Japanese Patent Publication No. Hei 6-502200, Japanese Patent Application Laid-Open No. Hei 5-70321, Patent No. 2593993, Japanese Patent Application Laid-Open No. Hei 9-3132, Japanese Patent Publication No. Hei 7-502053, Japanese Patent Application Laid-Open No. Hei 5-1177119, Japanese Patent Application Laid-Open No. Hei 4-283653, xe2x80x9cY. Iwasaki, K. Ishihara, N. Nakabayashi, C. Khang, J. H. Jeon, J. W. Lee, and H. B. Lee, J. Biomater. Sci., Polym, Edn., 9(8), p801-816 (1998)xe2x80x9d).
However, that it is possible to bond a copolymer having the aforementioned functional group to a polydialkylsiloxane/polyamide copolymer chemically by coating the latter on the former is not known.
Further, in the synthesis of a polydialkylsiloxane/polyamide copolymer, solvents such as pyridine, ethers such as dioxane and tetrahydrofuran and dimethylformamide are the only solvents that have been proposed for the case of the use of a dicarboxylic compound and a diamino compound as starting materials (Japanese Patent Application Laid-Open No. Hei 6-329791, Japanese Patent Publication No. Hei 1-23490, Japanese Patent Application Laid-Open No. Hei 7-292342). Chloroform is the only heretofore proposed example of a solvent for use in the case where a dicarboxylic acid chloride and a diamino compound are employed as starting materials (Japanese Patent Publication No. Hei 1-23490, Japanese Patent Application Laid-Open No. Hei 1-123824, Patent No. 2743432, Japanese Patent Application Laid-Open No. Hei 6-313864, Japanese Patent Application Laid-Open No. Hei 5-285216, Japanese Patent Application Laid-Open No. Hei 7-292342, Japanese Patent Application Laid-Open No. Hei 11-80360).
An intraocular lens, an example of the ophthalmic material, is a substitute for a crystalline lens which, for a variety of causes, suffers from cataract and became turbid. Recent operations for cataract have undergone improvements, utilizing the combination of phacoemulsification through a small incision and an intraocular lens made of a soft material.
By the way, intraocular lenses each constituted of a soft optical member and a plurality of fixation members for holding the optical member include three-piece ones and one-piece ones, and they are classified according to how the optical member and the fixation members, which are made from different materials, are connected. Further, in recent years, an intraocular lens being the integrally molded article of an optical member and fixation members, a so-called plate lens, has become known.
Unlike in the case of a conventional hard lens made of PMMA, a flexible lens cannot be subject to mechanical processing such as cutting or grind, because of softness of the material. Therefore, the optical member is made by the cast mold method in which an optical member molding material being for example a monomer, prepolymer, or oligomer is polymerized within a mold. Moreover, there is a problem that, when attaching the fixation members to the optical member, a technique other than conventional ones must be employed because it is also impossible to make pores in the optical member mechanically.
It is an object of the present invention to provide a novel polydialkylsiloxane/polyamide copolymer which is excellent in biocompatibility, mechanical strength, and thermal moldability and usable in a wide range of medical, ophthalmic, cosmetic, or electronic materials, and a process for producing the same.
It is another object of the present invention to provide a molded article which is excellent in biocompatibility, mechanical strength, and thermal moldability, substantially free from a solvent inevitably incorporated therein in the course of production, capable of keeping its transparency, and usable in a wide variety of medical, ophthalmic, cosmetic, or electronic materials.
It is another object of the present invention to provide an ophthalmic material such as contact lenses and intraocular lenses or a medical material such as antithrombotic materials which is excellent in biocompatibility, mechanical strength, thermal moldability, and hydrophilicity, substantially free from a solvent inevitably incorporated therein in the course of production, and capable of keeping its transparency.
It is still another object of the present invention to provide a cosmetic composition which, when applied onto the skin, shows excellent water resistance, oil resistance, durability, and ultraviolet ray blocking properties, has an excellent capability of keeping the shape of for example hair, and is usable in a variety of cosmetic products.
It is still another object of the present invention to provide an electronic material which is excellent in optical characteristics such as transparency, thermal moldability, and mechanical properties, shows insulation performance, and is usable in the electric, electronic, and optical device fields.
The inventors of the present invention made intensive studies to achieve the above-mentioned objects, and finally found that a novel polydialkylsiloxane/polyamide copolymer possessing excellent biocompatibility and high-level gas permeability together with high mechanical strength wherein such a reaction as crosslinking or decomposition which is caused under chemical, thermal, or mechanical stress with its amino, carboxylic acid chloride, or carboxylic acid group as an active site is inhibited from occurring. The copolymer can be obtained by reacting a siloxane oligomer having amino groups at both ends, an aromatic diamino compound, an aliphatic diamino compound, and an aromatic dicarboxylic acid chloride or aliphatic dicarboxylic acid chloride in a suitable ratio and reaction order, acylating part or all of the amino groups remaining at ends of the resulting copolymer, and carrying out alkylamidation, or by reacting with a compound having a hydroxyl group and/or an amino group after the dicarboxylic acid chloride has been reacted. The present invention was completed based on this finding.
Moreover, they also found that a copolymer of high transparency and excellent thermal moldability can be obtained through the use of, as a polymerization solvent to be employed in the synthesis of a polydialkylsiloxane/polyamide copolymer, a solvent selected from the group consisting of dimethylformamide, dimethylacetamide, tetrahydrofuran, dioxane, diglyme, acetonitrile, dimethoxyethane, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, and a mixture thereof. The present invention was completed based on this finding.
Further, they found that a molded article made of this novel polydialkylsiloxane/polyamide copolymer is stable against mechanical stress, has an enhanced stability against deterioration with time, and is largely improved in color change resistance and anti-degradation properties, and that it is easy to render this molded article hydrophilic. The molded article, ophthalmic material, medical material, and electronic material of the present invention were completed based on this findings.
Furthermore, the inventors found that cosmetics incorporating this novel polydialkylsiloxane/polyamide copolymer or its molded article show excellent water resistance, oil resistance, durability, and ultraviolet ray blocking properties and are effective in keeping the shape of for example hair. The cosmetic composition of the present invention was completed based on this finding.
According to the present invention, there is provided a polydialkylsiloxane/polyamide copolymer obtained by polymerizing
an amino compound represented by the formula (1) and having amino groups at both ends and a dialkylsiloxane chain:
H2Nxe2x80x94R1xe2x80x94(Si(R2)(R3)xe2x80x94O)n1-Si(R2)(R3)xe2x80x94R1xe2x80x94NH2xe2x80x83xe2x80x83(1)
wherein R1 represents a divalent organic group having 1 to 10 carbon atoms, R2 and R3 are the same or different, each representing an organic group having 1 to 7 carbon atoms, and n1 denotes an integer of 5 to 200,
a diamino compound represented by the formula (2):
H2Nxe2x80x94A1xe2x80x94NH2xe2x80x83xe2x80x83(2)
wherein A1 represents a divalent organic group having 1 to 20 carbon atoms,
and a dicarboxylic acid chloride represented by the formula (3):
ClCOxe2x80x94Bxe2x80x94COClxe2x80x83xe2x80x83(3)
wherein B represents a divalent organic group having 1 to 20 carbon atoms
to give a polydialkylsiloxane/polyamide copolymer (A) containing amino groups at the ends thereof in which the ratio of xe2x80x94R1xe2x80x94(Si(R2)(R3)xe2x80x94O)n1-Si(R2)(R3)xe2x80x94R1xe2x80x94 to xe2x80x94A1xe2x80x94 is within the range of 1:0.01xcx9c100, and reacting the copolymer (A) thus obtained with an acyl chloride having 2 to 8 carbon atoms.
Moreover, according to the present invention, there is provided a polydialkylsiloxane/polyamide copolymer obtained by polymerizing
an amino compound represented by the formula (1) and having amino groups at both ends and a dialkylsiloxane chain,
a diamino compound represented by the formula (2), and
a dicarboxylic acid chloride represented by the formula (3) to give a polydialkylsiloxane/polyamide copolymer (A) containing amino groups at the ends thereof in which the ratio of xe2x80x94R1xe2x80x94(Si(R2)(R3)xe2x80x94O)n1-Si(R2)(R3)xe2x80x94R1xe2x80x94 to xe2x80x94A1xe2x80x94 is within the range of 1:0.01xcx9c100, reacting the copolymer (A) thus obtained with a dicarboxylic acid chloride represented by the formula (3), and then with a compound selected from the group consisting of a monovalent hydroxyl group-containing compound having 1 to 8 carbon atoms, a monovalent amino group-containing compound having 1 to 8 carbon atoms, and a mixture thereof.
Furthermore, according to the present invention, there is provided a polydialkylsiloxane/polyamide copolymer which has a main chain represented by the formula (4), one end represented by the formula (5) and another end represented by the formula (6):
xe2x80x94(NHxe2x80x94Axe2x80x94NHCOxe2x80x94Bxe2x80x94CO)mxe2x80x83xe2x80x83(4)
xe2x80x94NHxe2x80x94Axe2x80x94NHxe2x80x94X2xe2x80x83xe2x80x83(5)
xe2x80x94X1xe2x80x83xe2x80x83(6)
wherein X1 and X2 each represents xe2x80x94COR4, xe2x80x94COxe2x80x94Bxe2x80x94COR5 (where R4 represents an organic group having 1 to 7 carbon atoms, R5 represents hydroxyl group, xe2x80x94OR6 or xe2x80x94NHR6 (where R6 represents an organic group having 1 to 7 carbon atoms) and B represents a divalent organic group having 1 to 20 carbon atoms) or hydrogen atom; A represents xe2x80x94R1xe2x80x94(Si(R2)(R3)xe2x80x94O)n1-Si(R2)(R3)xe2x80x94R1xe2x80x94 (where R1 represents a divalent organic group having 1 to 10 carbon atoms, R2 and R3 are the same or different, each representing an organic group having 1 to 7 carbon atoms, and n1 denotes an integer of 5 to 200) or a divalent organic group having 1 to 20 carbon atoms; B represents a divalent organic group having 1 to 20 carbon atoms; and m denotes an integer of 5 to 200,
wherein the ratio of xe2x80x94R1xe2x80x94(Si(R2)(R3)xe2x80x94O)n1-Si(R2)(R3)xe2x80x94R1xe2x80x94 as A to the divalent organic group having 1 to 20 carbon atoms as A is within the range of 1:0.01xcx9c100, and the proportion of X1 and X2 being hydrogen atoms is 10% or less relative to all the end groups in the copolymer.
Further, according to the present invention, there is provided a process for producing the above-described polydialkylsiloxane/polyamide copolymer in which, after a copolymer (A) having a main chain represented by the formula (4), one end represented by the formula (5) and another end represented by the formula (6) in which the ratio of xe2x80x94R1xe2x80x94(Si(R2)(R3)xe2x80x94O)n1-Si(R2)(R3)xe2x80x94R1xe2x80x94 as A to a divalent organic group having 1 to 20 carbon atoms as A is within the range of 1:0.01 xcx9c100 is obtained,
the step (I) in which the copolymer (A) is reacted with an acyl chloride having 2 to 8 carbon atoms to alkylamidate hydrogen atoms represented by X1 and X2 in the copolymer (A) so that the proportion of X1 and X2 being hydrogen atoms is 10% or less relative to all the end groups in the resulting copolymer, or
the step (II) in which the copolymer (A) is reacted with a dicarboxylic acid chloride represented by the formula (3), and then with a compound selected from the group consisting of a monovalent hydroxyl group-containing compound having 1 to 8 carbon atoms, a monovalent amino group-containing compound having 1 to 8 carbon atoms, and a mixture thereof so that, in the copolymer, the proportion of X1 and X2 being hydrogen atoms is 10% or less, is carried out.
Furthermore, according to the present invention, there is provided a molded article obtained by molding a molding material containing at least one kind of polydialkylsiloxane/polyamide copolymer described above.
The present invention further provides an ophthalmic or medical material comprising the above-described molded article.
The present invention further provides a cosmetic composition or electronic material containing at least either the polydialkylsiloxane/polyamide copolymer or the molded article.